The embodiments described herein relate to image-guided surgical techniques and more particularly apparatus and methods for localizing and/or determining the relative position of surgical instruments, such as ablation needles, during a medical procedure, such as an ablation procedure.
Image-guided therapy (IGT), which is also often referred to as image-guided intervention (IGI), has gained widespread attention and clinical acceptance for use in localizing tumors in abdominal organs. Procedures that utilize IGT include, but are not limited to, tumor biopsy, ablation, and resection. IGT describes the interactive use of medical images, often taken preoperatively, during a percutaneous medical procedure, and is often referred to as a “global positioning system” (GPS) for interventional radiology. By way of analogy, in an automobile GPS, the current position of a vehicle is accurately localized or “registered” onto an electronic roadmap that is updated as the automobile moves. The driver can use the GPS as a guide to see where their vehicle is, where it has been, where it is headed, and a planned route with which to follow to arrive at a selected destination. IGT allows a physician to accomplish essentially the same thing with one or more tracked medical instruments on a three-dimensional (3D) “roadmap” of highly detailed tomographic medical images of the patient that are acquired during and/or before the interventional procedure. Often, the key to an IGT procedure is the accurate registration between real “patient” space (e.g., during a procedure) and medical image space (e.g., preoperatively collected), such that an accurate absolute or relative position of a surgical instrument can be accurately determined.
In some IGT procedures, a 3D map or plan is developed using preoperative diagnostic images, possibly days before the actual procedure and in consultation with a variety of physicians in different disciplines. On the day of the IGT procedure, the position of the patient and the medical instruments are accurately localized or “registered” onto the preoperative images. As the physician moves the instrument, the precise location of its tip is updated on the 3D images. The exact location of the instrument is confirmed with a form of real-time imaging, including, but not limited to, intraoperative computed tomography (CT), two-dimensional (2D) fluoroscopy, or ultrasonic (US) imaging.
One type of IGT procedure includes Irreversible Electroporation (IRE), in which one or more ablation needles can be positioned within the patient. The ablation needles have to be positioned accurately within the patient's anatomy. Additionally, when more than one needle is used for treatment, relative distances between the needles determine the efficacy of the treatment. In IRE procedures, relative needle distances determine the size of an irreversible electroporation zone, and therefore the volume of tissue/tumor that is destroyed. Some surgeons rely on two dimensional (2D) ultrasound images to localize the position of the ablation needles and to determine the relative distances between the needles. An example of such a technique is disclosed in PCT Publication No. WO 2004/019799, entitled “Methods and systems for localizing of a medical imaging probe and for spatial registration and mapping of a biopsy needle during a tissue biopsy,” which is hereby incorporated by reference herein in its entirety. The lack of dimensionality in 2D ultrasound, however, renders known methods unable to localize more than one needle in a single ultrasound image.
Thus, a need exists for systems, apparatus and methods for localizing and/or determining the relative position of surgical instruments, generally, and of ablation needles in particular, for example, in a three-dimensional space and/or with respect to multiple instruments. A need also exists for a system, apparatus and method for localizing and/or determining when accounting for a relationship between a patient's pre-operative diagnostic images and the physical space in which the ultrasound images are captured.